CN110422231B

CN110422231B - vehicle control system

Info

Publication number: CN110422231B
Application number: CN201910338833.1A
Authority: CN
Inventors: 小城隆博; 国弘洋司; 入江亮; 赤塚久哉
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2018-04-27
Filing date: 2019-04-25
Publication date: 2021-11-05
Anticipated expiration: 2039-04-25
Also published as: DE102019205948B4; US20190331544A1; CN110422231A; DE102019205948A1; US11156515B2; JP2019189180A; JP6939692B2

Abstract

The present invention improves the accuracy of determining whether the driver state is the intervention state in the vehicle control system that performs automatic steering control. The vehicle control system includes: a torque sensor that detects the torque applied to the first position of the steering shaft as sensor detection torque; and a control device that performs automatic steering control. The upstream friction torque is the absolute value of the torque detected by the sensor due to the friction force acting on the steering shaft between the first position and the steering wheel when the steering shaft rotates. The control device repeatedly estimates the upstream friction torque, and variably sets the determination threshold value so as to be equal to or greater than the estimated value of the upstream friction torque. The control device determines the intervention state when the absolute value of the sensor detection torque is larger than the determination threshold value, and determines the non-intervention state in other cases.

Description

Vehicle control system

Technical Field

The present invention relates to a vehicle control system mounted on a vehicle. More particularly, the present invention relates to a vehicle control system that performs automatic steering control.

Background

Patent document 1 discloses a steering assist device mounted on a vehicle. The steering assist device performs lane maintenance control so that the vehicle travels along a lane. More specifically, the steering assist device determines an assist torque required for lane keeping control, and controls an eps (electric Power steering) motor so as to apply the assist torque to a steering mechanism.

The steering assist device also has a function of determining whether or not the driver has performed a steering operation. In this determination process, the friction torque Tg caused by the gear friction in the steering mechanism and the friction torque Tf caused by the gear friction in the steering column are considered. The friction torques Tg, Tf described above are estimated in advance by experiments and given as fixed values. The steering assist device determines that the driver has performed the steering operation when the assist torque based on the EPS motor is larger than the friction torque Tg and the steering torque detected by the torque sensor is larger than the friction torque Tf.

Patent document 2 discloses a method of recognizing an increase in gear friction inside a rack-driven EPS device. According to this method, a test current is caused to flow through a servomotor in the EPS device, and a change in the rotor position based on the test current is detected. An increase in gear friction is identified based on a result of a comparison of the detected change in rotor position with an expected value.

Patent document 1: japanese patent laid-open No. 2008-290679

Patent document 2: japanese patent laid-open No. 2014-172610

A vehicle control system that performs "automatic steering control" that automatically steers wheels of a vehicle is considered. When this automatic steering control is performed, there are cases where the driver intervenes in the steering operation of the vehicle. The state in which the driver intervenes in the steering manipulation is referred to as "intervention state (hands-on state)".

Determining whether the driver state is the intervention state is important for the automatic steering control. As an example, a case where a driving change request is issued from a vehicle control system is considered. If the vehicle control system ends the automatic steering control at a stage when the driver state has not reached the intervention state, the vehicle may be deviated from the lane. Preferably, the vehicle control system ends the automatic steering control after confirming that the driver's state has changed to the intervention state.

According to the technique disclosed in patent document 1, when determining whether or not the driver's state is the intervention state, the friction torque of the steering mechanism and the steering column due to gear friction is taken into consideration. The friction torque is estimated in advance by an experiment and given as a fixed value.

However, the magnitude of the friction torque fluctuates depending on the temperature environment and also depending on the aging of the components. Therefore, in the case where the friction torque is given as a fixed value, there is a high possibility that the friction torque deviates from the actual value. If the deviation is large, the accuracy of determining whether the driver state is the intervention state is degraded.

Disclosure of Invention

An object of the present invention is to provide a technique that can improve the accuracy of determination as to whether or not a driver's state is an intervention state in a vehicle control system that performs automatic steering control.

Claim 1 provides a vehicle control system mounted on a vehicle.

The vehicle includes:

a wheel;

a steering wheel; and

and a steering mechanism coupled to the steering wheel via a steering shaft, and configured to steer the wheels in response to a rotational operation of the steering wheel.

The vehicle control system includes:

a torque sensor for detecting a torque applied to the 1 st position of the steering shaft as a sensor detection torque; and

and a control device for performing automatic steering control for steering the wheels.

The upstream friction torque is an absolute value of the torque detected by the sensor due to a friction force acting on the steering shaft between the 1 st position and the steering wheel when the steering shaft is rotating.

The intervention state is a driver state in which a driver of the vehicle intervenes in a steering maneuver of the vehicle.

The non-intervention state is a driver state other than the intervention state described above.

The control device performs the following processing:

an upstream friction estimation process of repeatedly estimating the upstream friction torque based on the sensor detection torque at the time of steering of the wheel;

a threshold value setting process of variably setting a determination threshold value so as to be equal to or greater than the estimated value of the upstream friction torque; and

and a driver state determination process of determining that the driver state is the intervention state when the absolute value of the sensor detection torque is larger than the determination threshold, and determining that the driver state is the non-intervention state when the absolute value of the sensor detection torque is equal to or smaller than the determination threshold.

The invention according to claim 2 is characterized in that the above-described feature is provided in claim 1.

The control device determines whether the driver has evacuated his hands from the steering wheel.

The control device performs the upstream friction estimation process when the driver has evacuated the hand from the steering wheel during execution of the automatic steering control.

The invention according to claim 3 is characterized in that the above-described feature is provided in claim 2.

In the upstream friction estimation process, the control device may estimate an absolute value of the sensor detection torque at the time of starting rotation of the steering wheel by the automatic steering control as the upstream friction torque.

The invention according to claim 4 is characterized in that the above-described feature is provided in claim 2.

In the upstream friction estimation process, the control device may estimate, as the upstream friction torque, half of a hysteresis width of the sensor detection torque accompanying the automatic steering control.

According to the present invention, the vehicle control system performs the driver state determination process based on the comparison of the sensor detection torque and the determination threshold value. The vehicle control system variably sets the determination threshold value according to the fluctuation of the upstream friction torque. More specifically, the vehicle control system repeatedly estimates the upstream friction torque, and sets the determination threshold value so that the estimated value of the upstream friction torque becomes equal to or greater than the estimated value. This improves the accuracy of the driver state determination process.

Drawings

Fig. 1 is a conceptual diagram for explaining an outline of a vehicle control system according to an embodiment of the present invention.

Fig. 2 is a block diagram showing a specific configuration example of a vehicle and a vehicle control system according to an embodiment of the present invention.

Fig. 3 is a block diagram showing a functional configuration of a control device of a vehicle control system according to an embodiment of the present invention.

Fig. 4 is a conceptual diagram for explaining a reverse input friction estimation method in the embodiment of the present invention.

Fig. 5 is a conceptual diagram for explaining a reverse input friction estimation method in the embodiment of the present invention.

Fig. 6 is a conceptual diagram for explaining a forward input friction estimation method in the embodiment of the present invention.

Fig. 7 is a block diagram showing an example of a functional configuration of the variable threshold setting unit according to the embodiment of the present invention.

Fig. 8 is a block diagram showing another example of the functional configuration of the variable threshold setting unit according to the embodiment of the present invention.

Fig. 9 is a flowchart showing an example of the variable threshold setting process according to the embodiment of the present invention.

Fig. 10 is a flowchart showing an example 1 of driving control in the embodiment of the present invention.

Fig. 11 is a flowchart showing an example 2 of the driving control in the embodiment of the present invention.

Fig. 12 is a flowchart showing example 3 of the driving control in the embodiment of the present invention.

Fig. 13 is a block diagram showing a functional configuration of a control device of a vehicle control system according to an embodiment of the present invention.

Fig. 14 is a conceptual diagram for explaining example 1 of the parameter estimation process in the embodiment of the present invention.

Fig. 15 is a conceptual diagram for explaining example 2 of the parameter estimation processing in the embodiment of the present invention.

Fig. 16 is a flowchart for explaining example 2 of the parameter estimation process in the embodiment of the present invention.

Description of reference numerals

A vehicle; a wheel; a steering wheel (steering wheel); a steering shaft; a steering mechanism; a steering column; a vehicle control system; an EPS device; a running gear; a sensor group; a steering wheel angle sensor; a torque sensor; a steering angle sensor; an HMI unit; driving environment information obtaining means; a driver monitor; a control device; a driving control section; a steering control section; a driving control section; a driver state determination section; a variable threshold setting section; a hands-off determination section; an upstream friction estimating section; 153.. a threshold setting section; a driver steering torque estimation section; a parameter estimation section; driving environment information.

Detailed Description

Embodiments of the present invention will be described with reference to the accompanying drawings.

1. Overview of vehicle control System

Fig. 1 is a conceptual diagram for explaining an outline of a vehicle control system 10 according to the present embodiment. The vehicle control system 10 is mounted on the vehicle 1, and controls the operation of the vehicle 1. More specifically, the vehicle control system 10 performs at least "automatic steering control" that automatically controls the steering of the vehicle 1. The steering operation of the vehicle 1 refers to steering of the wheels 2 of the vehicle 1.

For example, the vehicle control system 10 determines a target path PT (target trajectory) as shown in fig. 1. Then, the vehicle control system 10 performs the automatic steering control so that the vehicle 1 follows the target path PT. Such an automatic steering control is performed in Lane keeping Assist control (LTA), automatic driving control, and the like. In the case of the automatic driving control, the vehicle control system 10 performs not only the automatic steering control but also "automatic travel control" that automatically controls the travel (acceleration and deceleration) of the vehicle 1.

Fig. 2 is a block diagram showing a specific configuration example of the vehicle 1 and the vehicle control system 10 according to the present embodiment.

The vehicle 1 includes wheels 2, a Steering wheel 3(Steering wheel), a Steering shaft 4, a Steering mechanism 5, and a Steering column 6. The steering wheel 3 is an operation member for the driver to perform a steering operation. One end of the steering shaft 4 is coupled to the steering wheel 3, and the other end thereof is coupled to the steering mechanism 5. The steering mechanism 5 steers the wheels 2 in accordance with a rotating operation of the steering wheel 3. Specifically, the steering mechanism 5 includes a pinion gear coupled to the steering shaft 4, a rack bar that meshes with the pinion gear, and a tie rod that couples the rack bar and the wheel 2. The rotation of the steering wheel 3 is transmitted to the pinion gear via the steering shaft 4. The rotational motion of the pinion is converted into the linear motion of the rack bar, thereby changing the steering angle θ of the wheel 2.

The vehicle control system 10 includes an eps (electric Power steering) device 20, a travel device 30, a sensor group 40, an hmi (human Machine interface) unit 50, a driving environment information acquisition device 60, and a control device 100.

The EPS device 20 includes an electric motor, and the wheels 2 are steered by rotation of the electric motor. For example, the electric motor is coupled to the rack bar via a conversion mechanism. When the rotor of the electric motor rotates, the conversion mechanism converts the rotational motion thereof into the linear motion of the rack bar. Thereby, the steering angle θ of the wheel 2 changes. The EPS device 20 is not limited to the rack assist type. For example, the EPS device 20 may be a steering column assist type. The operation of the EPS device 20 is controlled by the control device 100.

The running device 30 includes a driving device and a braking device. The driving device is a power source that generates driving force. Examples of the driving device include a motor and an engine. The brake device generates a braking force. The operation of the traveling device 30 is controlled by the control device 100.

The sensor group 40 detects the state of the vehicle 1. For example, the sensor group 40 includes a steering wheel angle sensor 41, a torque sensor 42, and a steering angle sensor 43.

The steering wheel angle sensor 41 detects a steering angle MA, which is a steering angle of the steering wheel 3. The steering wheel angle sensor 41 outputs information indicating the steering wheel angle MA to the control device 100.

The torque sensor 42 detects the torque applied to the steering shaft 4. More specifically, the torque sensor 42 is provided at a predetermined position (1 st position) of the steering shaft 4, and detects a torque applied at the predetermined position. Hereinafter, the torque detected by the torque sensor 42 is referred to as "sensor detection torque MT". Torque sensor 42 outputs information indicating sensor detection torque MT to control device 100.

The steering angle sensor 43 detects a steering angle θ of the wheels 2. For example, the steering angle sensor 43 calculates the steering angle θ from the rotation angle of the electric motor of the EPS device 20. The steering angle sensor 43 outputs information indicating the steering angle θ to the control device 100.

The HMI unit 50 is an interface for providing information to the driver and also receiving information from the driver. Specifically, the HMI unit 50 has an input device and an output device. Examples of the input device include a touch panel, a switch, and a microphone. Examples of the output device include a display device and a speaker.

The driving environment information acquisition device 60 acquires "driving environment information ENV" indicating the driving environment of the vehicle 1. The driving environment information ENV includes position information, map information, surrounding condition information, vehicle state information, and the like. The position information is information indicating the position of the vehicle 1, and is obtained by using, for example, a gps (global Positioning system). The map information indicates lane arrangement and road shape. The surrounding condition information is information indicating the surrounding condition of the vehicle 1, and is obtained by using an external sensor such as a camera, a laser radar, or a radar. For example, the surrounding situation information includes information on surrounding vehicles around the vehicle 1 and white lines. The vehicle state information includes a vehicle speed, a lateral acceleration, a yaw rate, and the like. These pieces of vehicle state information are acquired by the sensor group 40. Driving environment information acquisition device 60 transmits acquired driving environment information ENV to control device 100.

The control device 100 is a microcomputer including a processor and a memory. The Control device 100 is also referred to as an ecu (electronic Control unit). The processor executes a control program stored in the memory, thereby implementing various processes based on the control device 100. Hereinafter, the functional configuration of the control device 100 according to the present embodiment will be described in more detail.

2. Functional structure of control device

Fig. 3 is a block diagram showing a functional configuration of the control device 100 according to the present embodiment. The control device 100 includes a driving control unit 110, a driver state determination unit 140, and a variable threshold setting unit 150 as functional blocks. These functional blocks are realized by the processor of the control device 100 executing a control program stored in the memory.

2-1. driving control part 110

The driving control unit 110 controls driving of the vehicle 1. More specifically, the driving control unit 110 includes a steering control unit 120 that controls steering of the vehicle 1, and a travel control unit 130 that controls travel (acceleration and deceleration) of the vehicle 1.

The steering control unit 120 performs steering assist control for assisting a steering operation performed by the driver. Specifically, the steering control unit 120 calculates the assist torque based on the sensor detection torque MT and the vehicle speed. Then, the steering control unit 120 controls the operation of the EPS device 20 so as to obtain the assist torque. This reduces the steering load on the driver.

The steering control unit 120 performs "automatic steering control" for automatically steering the wheels 2. In the automatic steering control, the EPS device 20 is also used. Specifically, the steering control unit 120 determines a steering angle command value θ h, which is a target value of the steering angle θ of the wheels 2. The steering control unit 120 acquires information on the steering angle θ from the steering angle sensor 43. Alternatively, the steering control unit 120 may calculate the steering angle θ from the steering wheel angle MA. The steering control unit 120 controls the operation of the EPS device 20 so that the steering angle θ follows the steering angle command value θ h.

For example, the steering control unit 120 performs the automatic steering control so that the vehicle 1 travels following the target path PT (see fig. 1). For this purpose, the steering control portion 120 calculates the target path PT and the target path steering angle θ PT based on the driving environment information ENV. The target path steering angle θ PT is a steering angle θ necessary for the vehicle 1 to travel so as to follow the target path PT. Various methods have been proposed as a method for calculating the target path PT and the target path steering angle θ PT. In the present embodiment, the calculation method is not particularly limited. The steering control unit 120 sets the steering angle command value θ h to the target path steering angle θ pt, and controls the operation of the EPS device 20 so that the steering angle θ follows the target path steering angle θ pt. Thereby, the vehicle 1 travels so as to follow the target path PT. Such automatic steering control is performed in automatic driving control, LTA, and the like.

The travel control unit 130 performs "automatic travel control" for automatically controlling the travel of the vehicle 1. The automatic travel control includes acceleration control and deceleration control. The travel control unit 130 performs automatic travel control by controlling the operation of the travel device 30 (driving device, braking device). For example, the travel control unit 130 performs automatic travel control so that the vehicle 1 travels following the target route PT.

The driving control unit 110 may perform "automatic driving control" including both the automatic steering control and the automatic traveling control described above.

The driving control unit 110 outputs various notifications to the driver through the HMI unit 50 (output device). Examples of the notification include a warning and a driving change request (TD). The driving change request requests the driver to start manual driving.

The driver can also turn on/off driving control (automatic steering control, automatic travel control, automatic driving control) by the driving control unit 110 using the HMI unit 50 (input device).

2-2. driver state determination section 140

When the automatic steering control by the driving control portion 110 is performed, there is a case where the driver intervenes in the steering of the vehicle 1. Hereinafter, the driver state in which the driver intervenes in the steering operation of the vehicle 1 is referred to as "intervention (hung-ON) state". For example, a state in which the driver performs a steering operation, i.e., actively operates the steering wheel 3, is an intervention state. Further, the state in which the driver holds the steering wheel 3 against the automatic steering control by the driving control portion 110 is also the intervening state.

On the other hand, a driver state in which the driver does not intervene in the steering operation of the vehicle 1 is hereinafter referred to as a "non-intervention (HANDS-OFF) state". The non-intervention state may be said to be a driver state other than the intervention state.

Determining whether the driver state is the intervention state or the non-intervention state is important for the automatic steering control. As an example, a case where the driving control unit 110 issues the above-described driving change request is considered. If the driving control unit 110 ends the automatic steering control at a stage when the driver state has not yet changed to the intervention state, the vehicle 1 may be deviated from the lane. Preferably, the driving control unit 110 terminates the automatic steering control after confirming that the driver's state has changed to the intervention state.

For this purpose, a driver state determination unit 140 is provided. The driver state determination unit 140 performs "driver state determination processing" for determining whether the driver state is the intervention state or the non-intervention state. More specifically, the driver state determination unit 140 compares the sensor detection torque MT detected by the torque sensor 42 with the "determination threshold TH". The driver state determination unit 140 determines that the driver state is the intervention state when the absolute value of the sensor detection torque MT is greater than the determination threshold TH (| MT | > TH). On the other hand, when the absolute value of the sensor detection torque MT is equal to or less than the determination threshold TH (| MT | ≦ TH), the driver state determination unit 140 determines that the driver state is the non-intervention state.

2-3 variable threshold setting unit 150

The variable threshold setting unit 150 sets the determination threshold TH used in the driver state determination process described above. The setting of the determination threshold TH should be noted by a frictional force generated by a gear or the like. This is because the frictional torque caused by the frictional force is included in the sensor detection torque MT.

In the present embodiment, attention is paid particularly to "upstream frictional force" upstream of the torque sensor 42. More specifically, the upstream frictional force is a frictional force acting on the steering shaft 4 between the installation position (1 st position) of the torque sensor 42 and the steering wheel 3 when the steering shaft 4 rotates. The upstream frictional force is generated by, for example, a gear or the like in the steering column 6. When the steering shaft 4 rotates, the sensor detection torque MT detected by the torque sensor 42 includes a friction torque due to an upstream friction force. Hereinafter, the absolute value of the component of the sensor detection torque MT due to the upstream friction force is referred to as "upstream friction torque TF".

Consider a state in which the driver evacuates the HANDS from the steering wheel 3 (HANDS-FREE state). When the driving control unit 110 steers the wheels 2 by the automatic steering control, the steering shaft 4 and the steering wheel 3 are also rotated. At this time, the torque sensor 42 detects the upstream friction torque TF due to the upstream friction force as the sensor detection torque MT. That is, although the driver is evacuated from the steering wheel 3, the upstream friction torque TF, which is not zero, is detected as the sensor detection torque MT.

In order to prevent erroneous determination of the driver's state, the determination threshold TH is set to be equal to or higher than the upstream friction torque TF. However, the magnitude of the upstream friction torque TF is not constant but varies. Specifically, the magnitude of the upstream friction torque TF varies depending on the temperature environment and also depending on the aging of the components.

Therefore, according to the present embodiment, the variable threshold setting unit 150 variably sets the determination threshold TH according to the variation of the upstream friction torque TF. More specifically, the variable threshold setting unit 150 repeatedly estimates the upstream friction torque TF. Then, the variable threshold setting unit 150 sets the determination threshold TH so as to be equal to or larger than the estimated value of the upstream friction torque TF. This improves the accuracy of the driver state determination process. This leads to an improvement in the reliability for the vehicle control system 10.

Hereinafter, the variable threshold setting process performed by the variable threshold setting unit 150 according to the present embodiment will be described in more detail.

3. Variable threshold setting process

3-1. reverse input friction estimation method

First, a method of estimating the upstream friction torque TF in a hand-free state where the driver has evacuated the hands from the steering wheel 3 will be described. Hereinafter, this method is referred to as a "reverse input friction estimation method".

Fig. 4 is a conceptual diagram for explaining the reverse input friction estimation method. In the hands-free state, the driving control unit 110 performs automatic steering control to steer the wheels 2. Fig. 4 shows a variation in the sensor detection torque MT when the wheels 2 are steered by the automatic steering control in the hands-free state. The vertical axis represents the sensor detection torque MT, and the horizontal axis represents the steering parameter, which indicates the steering of the wheels 2. In the example shown in fig. 4, the steering wheel angle MA is used as the steering parameter. Instead of the steering wheel angle MA, the steering angle θ, the yaw rate, or the lateral acceleration may be used.

As shown in fig. 4, when the wheels 2 are steered in a free-hand state, the steering wheel 3 is turned, and therefore torque is generated in a direction opposite to the direction in which the driver performs the steering operation. More specifically, the sensor detection torque MT becomes a negative value when the steering angle MA increases, and becomes a positive value when the steering angle MA decreases. In either case, the absolute value of the sensor detection torque MT is almost constant. This constant value corresponds to the upstream friction torque TF. The upstream friction torque TF may be an absolute value of the sensor detection torque MT when the steering wheel 3 starts to rotate by the automatic steering control in the hand free state.

In addition, as shown in fig. 4, the hysteresis width HIS of the sensor detection torque MT is almost constant regardless of the steering wheel angle MA. Half of the hysteresis width HIS corresponds to the upstream friction torque TF.

The variable threshold setting unit 150 estimates the upstream friction torque TF based on the sensor detection torque MT when the wheels 2 are steered by the automatic steering control. Specifically, the variable threshold setting unit 150 estimates the absolute value of the sensor detection torque MT at the time of starting rotation of the steering wheel 3 by the automatic steering control as the upstream friction torque TF. Alternatively, the variable threshold setting unit 150 estimates half of the hysteresis width HIS of the sensor detection torque MT accompanying the automatic steering control as the upstream friction torque TF. When the hysteresis width HIS is used, the influence of noise and vibration components can be removed.

Fig. 5 shows a case where the upstream friction torque TF increases. If the upstream friction torque TF increases, the hysteresis width HIS also increases. The variable threshold setting unit 150 repeatedly executes the estimation process, and can obtain the latest value of the upstream friction torque TF.

3-2. positive input friction estimation method

Next, a method of estimating the upstream friction torque TF in a steering state where the driver performs a steering operation will be described. Hereinafter, this method is referred to as a "forward input friction estimation method".

Fig. 6 is a conceptual diagram for explaining the forward input friction estimation method. The format of fig. 6 is the same as that of fig. 4 already given. The MA-MT characteristic in the steering state is represented by a lissajous waveform as is well known. Unlike the case of fig. 4, the absolute value of the sensor detection torque MT is not almost constant. The trend of the variation of the sensor detection torque MT is also different from that in fig. 4. Specifically, as the steering wheel angle MA increases, the sensor detection torque MT also increases. On the other hand, when the steering wheel angle MA decreases, the sensor detection torque MT decreases.

The variable threshold setting unit 150 estimates the upstream friction torque TF based on the sensor detection torque MT when the wheels 2 are steered by the steering operation. Specifically, the variable threshold setting unit 150 estimates half of the hysteresis width HIS of the sensor detection torque MT at the steering angle midpoint (MA ═ 0) as the upstream friction torque TF.

However, the upstream friction torque TF estimated by the forward input friction estimation method may also include the influence of the downstream friction force. The downstream frictional force is a frictional force on the wheel 2 side of the torque sensor 42, and is generated in a gear of the steering mechanism 5, for example. The downstream friction torque is an absolute value of a component of the sensor detection torque MT due to the downstream friction force, and is calculated in advance. The variable threshold setting unit 150 may estimate a value obtained by subtracting the downstream friction torque from half the hysteresis width HIS as the upstream friction torque TF.

3-3 functional configuration example of variable threshold setting section

Fig. 7 is a block diagram showing an example of the functional configuration of the variable threshold setting unit 150. The variable threshold setting unit 150 includes a hands-off determination unit 151, an upstream friction estimation unit 152, and a threshold setting unit 153.

The hands-off determination unit 151 performs "hands-off determination processing". In the hands-off determination process, the hands-off determination unit 151 determines whether or not the driver has evacuated his hands from the steering wheel 3. That is, the hands-off determination unit 151 determines whether the driver's state is a hands-free state.

For example, the hands-off determination unit 151 detects a variation tendency of the torque MT based on a sensor during steering of the wheels 2, and performs hands-off determination processing. As shown in fig. 4, in the case of the hands-free state, the sensor detection torque MT becomes a negative value when the steering angle MA increases, and becomes a positive value when the steering angle MA decreases. On the other hand, in the case of fig. 6, the sensor detection torque MT increases when the steering angle MA increases, and decreases when the steering angle MA decreases. Therefore, it is possible to determine whether the driver's state is a free-hand state based on the tendency of the sensor to detect the fluctuation of the torque MT.

Fig. 8 shows a modification. In the modification, the vehicle control system 10 further includes a driver monitor 70. The driver monitor 70 includes a steering touch sensor, a gap sensor, a camera, and the like. The hands-off determination unit 151 determines whether or not the driver has evacuated his hands from the steering wheel 3 based on the measurement result of the driver monitor 70.

The upstream friction estimating unit 152 performs "upstream friction estimating processing". In the upstream friction estimation process, the upstream friction estimation unit 152 repeatedly estimates the upstream friction torque TF based on the sensor detection torque MT during steering of the wheels 2. In particular, when the driver removes his hands from the steering wheel 3 while the automatic steering control is being executed, the upstream friction estimating unit 152 estimates the upstream friction torque TF by inputting the friction estimating method in the reverse direction (see fig. 4 and 5). This enables the upstream friction torque TF to be estimated with high accuracy.

When the driver is performing the steering operation, the upstream friction estimating unit 152 may estimate the upstream friction torque TF by a forward input friction estimating method (see fig. 6).

The threshold setting unit 153 performs "threshold setting processing". In the threshold setting process, the threshold setting unit 153 variably sets the determination threshold TH based on the estimated upstream friction torque TF. More specifically, the threshold setting unit 153 sets the determination threshold TH so that the estimated value of the upstream friction torque TF is equal to or greater than the estimated value. For example, the determination threshold TH is expressed by the following equation (1).

Formula (1): TH is TF + alpha is less than or equal to LIM

In equation (1), the parameter α is a difference value in consideration of an error, and the parameter LIM is a set upper limit value. When the determination threshold TH exceeds the set upper limit LIM, the threshold setting unit 153 may notify the driver of the abnormality through the HMI unit 50.

3-4 flow example of variable threshold setting processing

Fig. 9 is a flowchart showing an example of the variable threshold setting process by the variable threshold setting unit 150. The processing flow shown in fig. 9 is repeatedly executed in units of a constant cycle.

In step S10, the hands-off determination unit 151 performs the hands-off determination process. In the case where the driver has evacuated the hands from the steering wheel 3 (step S10; yes), the process proceeds to step S20. Otherwise (step S10; NO), the process advances to step S40.

In step S20, the upstream friction estimating unit 152 estimates the upstream friction torque TF by a reverse input friction estimating method (see fig. 4 and 5). After that, the process advances to step S30.

In step S30, the upstream friction estimating unit 152 sets the flag FL to "1". The flag FL indicates the presence or absence of the history of the reverse input friction estimation. The initial value of the flag FL is "0". After that, the process advances to step S60.

In step S40, the upstream friction estimating unit 152 determines whether or not the flag FL is "0". If the flag FL is "0" (step S40; yes), the process proceeds to step S50. On the other hand, if the flag FL is "1" (step S40; no), the process in the current cycle is ended.

In step S50, the upstream friction estimating unit 152 estimates the upstream friction torque TF by a forward input friction estimating method (see fig. 6). After that, the process advances to step S60.

In step S60, the threshold setting unit 153 sets the determination threshold TH according to the above expression (1). After that, the process advances to step S70.

In step S70, the threshold setting unit 153 compares the determination threshold TH with the set upper limit LIM. If the determination threshold TH is equal to or less than the set upper limit LIM (step S70; yes), the process in the current cycle is ended. On the other hand, when the determination threshold TH exceeds the set upper limit LIM (step S70; NO), the process proceeds to step S80.

In step S80, the variable threshold setting unit 150 performs error processing. For example, the variable threshold setting unit 150 notifies the driver of an abnormality through the HMI unit 50. In addition, the driving control unit 110 may notify the "end of the automatic steering control" to the driver through the HMI unit 50. In this case, the driving control unit 110 ends the automatic steering control after confirming that the intervention state continues for a predetermined time.

According to the processing flow shown in fig. 9, the determination threshold TH changes, for example, as follows. First, the driver performs manual driving. At this time, the determination threshold TH is set based on the upstream friction torque TF estimated by the forward input friction estimation method. After that, the automatic driving control by the driving control portion 110 is started. When the automatic driving control is started, the determination threshold TH is set based on the upstream friction torque TF estimated by the reverse input friction estimation method. That is, the accuracy of the determination threshold TH is improved. After that, the determination threshold TH is repeatedly updated.

4. Various examples of driving control

The driving control unit 110 performs driving control based on the result of the driver state determination process performed by the driver state determination unit 140. Various examples of the driving control will be described below.

4-1 example 1

Fig. 10 is a flowchart showing an example 1 of the driving control. The processing flow shown in fig. 10 is repeatedly executed in units of a constant cycle.

In step S100, the driving control unit 110 determines whether or not the driving control is turned on. The driver can turn on/off the driving control using the HMI unit 50. If the driving control is off (step S100; no), the process is ended. On the other hand, when the drive control is turned on (step S100; YES), the process proceeds to step S110.

In step S110, the driving control unit 110 refers to the result of the driver state determination process. If the driver state is the intervention state or if the intervention state continues for a constant time (step S110; yes), the process proceeds to step S120. On the other hand, when the driver state is the non-intervention state or the non-intervention state continues for a constant time (step S110; no), the process proceeds to step S130.

In step S120, the driving control unit 110 performs lane keeping assist control (LTA). In step S130, the driving control unit 110 performs the automatic driving control. As described above, according to example 1, the driving control unit 110 switches the driving control between the lane keeping assist control and the automatic driving control according to the driver's state.

4-2 example 2

Fig. 11 is a flowchart showing a 2 nd example of the driving control. The processing flow shown in fig. 11 is repeatedly executed in units of a constant cycle.

In step S200, the driving control unit 110 performs driving control on the assumption of the intervention state. As the driving control assuming the intervention state, a steering assist control during manual driving, a lane keeping assist control (LTA), and the like are exemplified.

In step S210, the driving control unit 110 refers to the result of the driver state determination process. If the driver state is the non-intervention state or if the non-intervention state continues for a constant time (step S210; yes), the process proceeds to step S220. Otherwise (step S210; no), the process in the current cycle is ended.

In step S220, the driving control unit 110 issues a warning to the driver through the HMI unit 50. For example, the driving control unit 110 outputs a warning message such as "please hold the steering wheel". This expects the driver state to return to the intervention state.

4-3 example 3

Fig. 12 is a flowchart showing example 3 of the driving control. The processing flow shown in fig. 12 is repeatedly executed in units of a constant cycle.

In step S300, the driving control unit 110 performs the automatic driving control.

In step S310, the driving control unit 110 notifies the driver of a driving change request through the HMI unit 50. After that, the process advances to step S320.

In step S320, the driving control unit 110 refers to the result of the driver state determination process. If the driver state is the intervention state or if the intervention state continues for a constant time (step S320; yes), the process proceeds to step S330. Otherwise (step S320; no), the process in the current cycle is ended.

In step S330, the driving control unit 110 ends the automatic driving control. At this time, the driving control unit 110 may output a confirmation message such as "switch to manual driving" through the HMI unit 50.

5. Effect

As described above, according to the present embodiment, the vehicle control system 10 performs the driver state determination process based on the comparison between the sensor detection torque MT and the determination threshold TH. The vehicle control system 10 also variably sets the determination threshold TH according to the variation of the upstream friction torque TF. More specifically, the vehicle control system 10 repeatedly estimates the upstream friction torque TF and sets the determination threshold TH so as to be equal to or larger than the estimated value of the upstream friction torque TF. This improves the accuracy of the driver state determination process.

As comparative example 1, a technique disclosed in the above-mentioned patent document 1 (japanese patent application laid-open No. 2008-290679) is considered. According to comparative example 1, the upstream friction torque TF is estimated in advance by an experiment and set to a fixed value. However, the actual upstream friction torque TF fluctuates, and the set value of the upstream friction torque TF deviates from the actual value. If the deviation is large, the accuracy of the driver state determination process is reduced.

As comparative example 2, the determination threshold TH is set to a fixed value that is sufficiently large or small in consideration of the expected variation in the upstream friction torque TF. In this case, the set value of the upstream friction torque TF is still deviated from the actual value, and therefore the accuracy of the driver state determination process is degraded.

If the determination threshold TH is set to a value too small, the following problem occurs. For example, the driver performs a steering operation in response to a driving change request. If the driver state is determined to be the intervention state, the automatic steering control is terminated. However, in the case where the determination threshold TH is small, there is a possibility that the driver state is erroneously determined to be the intervention state although the driver state is still the non-intervention state. When the automatic steering control is ended in a state where such an erroneous determination occurs, the vehicle 1 may be deviated from the lane.

In addition, when the determination threshold TH is set to a too large value, the following problem occurs. For example, the driver performs a steering operation in response to a driving change request. The automatic steering control continues until a timing at which it is determined that the driver's state is the intervention state. The larger the determination threshold TH is, the later the timing is, and therefore the driver feels discomfort in the steering operation. The avoidance behavior of the vehicle 1 is also considered to be delayed when the driver performs the steering operation early in order to avoid a collision. That is, in the case where the determination threshold TH is too large, controllability with respect to steering operation may be degraded.

According to the present embodiment, the accuracy of the driver state determination process is improved. Therefore, erroneous determination of the driver's state is suppressed. In addition, a decrease in controllability for steering is suppressed. This leads to an improvement in reliability with respect to the vehicle control system 10.

6. Estimation of driver steering torque

The control device 100 according to the present embodiment may have a function of estimating the driver steering torque MTD. The driver steering torque MTD is a torque applied by the driver to rotate the steering wheel 3, and indicates the intensity of the steering operation performed by the driver. The driver state determination unit 140 may perform the driver state determination process using the estimated driver steering torque MTD instead of the sensor detection torque MT.

Fig. 13 is a block diagram showing a functional configuration of the control device 100. The control device 100 includes a driver steering torque estimation unit 160 and a parameter estimation unit 170 in addition to the functional configurations already described. These functional blocks are realized by the processor of the control device 100 executing a control program stored in the memory.

The driver steering torque estimation unit 160 performs "driver steering torque estimation processing" for estimating the driver steering torque MTD. The method of estimating the driver steering torque MTD is not particularly limited. For example, the driver steering torque estimation portion 160 estimates the driver steering torque MTD using a model of the steering system. In this case, the driver steering torque estimation portion 160 can estimate the driver steering torque MTD based on the sensor detection torque MT, the motor rotation angle δ, and the motor rotation angular velocity d δ/dt. The motor rotation angle δ is a rotation angle of a rotor of an electric motor of the EPS device 20, and is detected by a rotation angle sensor not shown. The motor rotation angular velocity d δ/dt is obtained by differentiating the motor rotation angle δ.

The model of the steering system used in the driver steering torque estimation process may include mechanical parameters that change in accordance with the external environment. A typical example of the mechanical parameter that changes in correspondence with the external environment is a mechanical friction term that changes in correspondence with the outside air temperature. In the case where such a mechanical parameter is fixed to a nominal value, that is, in the case where a nominal model is used regardless of variations in the external environment, the accuracy of estimating the driver steering torque MTD decreases.

In order to suppress such a decrease in the estimation accuracy of the driver steering torque MTD, a parameter estimation unit 170 is provided. The parameter estimation unit 170 performs "parameter estimation processing" for estimating a mechanical parameter corresponding to the external environment. Hereinafter, the estimated machine parameter is referred to as "estimated parameter F". The parameter estimation portion 170 outputs the estimation parameter F to the driver steering torque estimation portion 160. The driver steering torque estimation portion 160 performs driver steering torque estimation processing using a model based on the estimation parameter F. This suppresses a decrease in the estimation accuracy of the driver steering torque MTD.

The parameter estimation unit 170 performs parameter estimation processing in units of a constant cycle. The estimated parameter F is updated every time the parameter estimation process is performed. The parameter estimation unit 170 may store a history of the estimated parameter F from an initial value in the memory of the control device 100.

An example of the parameter estimation process by the parameter estimation unit 170 will be described below.

6-1 example 1

Fig. 14 is a conceptual diagram for explaining example 1 of the parameter estimation process. In example 1, a mechanical parameter (e.g., mechanical friction term) that changes in accordance with the outside air temperature T is considered. In this case, the estimated parameter F is represented by a function of the outside air temperature T. The function, i.e., the correspondence between the outside air temperature T and the estimated parameter F is given by a map or a numerical expression. The parameter estimation unit 170 receives information of the outside air temperature T detected by an outside air temperature sensor (not shown). Then, parameter estimation unit 170 acquires estimated parameter F based on outside air temperature T and the above function.

When the outside air temperature sensor has failed, the parameter estimation unit 170 may stop the parameter estimation process. In this case, parameter estimation unit 170 outputs estimated parameter F immediately before the failure of the outside air temperature sensor. Since the outside air temperature does not change rapidly, the use of the estimation parameter F immediately before the failure of the outside air temperature sensor can suppress a decrease in the estimation accuracy of the driver steering torque MTD.

When the failure of the outside air temperature sensor continues for a constant period or longer, there is a possibility that the outside air temperature changes during the constant period. Therefore, in this case, the parameter estimation unit 170 may gradually change the output estimated parameter F to an initial value.

6-2 example 2

Fig. 15 is a conceptual diagram for explaining example 2 of the parameter estimation process. In example 2, the parameter estimation unit 170 includes a sensor detection torque estimation model 171.

The sensor detection torque estimation model 171 is a model for estimating the sensor detection torque MT detected by the torque sensor 42. The sensor detection torque estimation model 171 is obtained by deforming a model used when the driver steering torque estimation unit 160 estimates the driver steering torque MTD.

The parameter estimation unit 170 sets the model parameters of the sensor detection torque estimation model 171 to various values, and estimates the sensor detection torque MT. The parameter estimation unit 170 compares the estimated value of the sensor detection torque MT with the actual value of the sensor detection torque MT. Then, the parameter estimation unit 170 outputs the model parameter that has obtained the estimated value closest to the actual value as the estimated parameter F.

Fig. 16 is a flowchart for explaining example 2 of the parameter estimation process. The processing flow shown in fig. 16 is repeatedly executed in units of a constant cycle.

In step S400, the parameter estimation portion 170 determines whether or not a steering operation is being performed by the driver. For example, the parameter estimation unit 170 compares the absolute value of the driver steering torque MTD estimated by the driver steering torque estimation unit 160 with a predetermined threshold value. When the absolute value of the driver steering torque MTD is larger than a predetermined threshold value, the parameter estimation unit 170 estimates that the steering operation is being performed by the driver. Alternatively, the parameter estimation unit 170 may determine whether or not the driver is performing the steering operation based on the measurement result of the driver monitor 70 (see fig. 8).

When the steering operation is being performed by the driver (step S400; yes), there is a possibility that the estimation accuracy of the sensor detection torque MT is lowered. Therefore, in this case, the parameter estimation unit 170 outputs the previous value of the estimation parameter F without performing the parameter estimation process (step S410).

On the other hand, when the steering operation is not performed by the driver (step S400; NO), the parameter estimation unit 170 performs the parameter estimation process. The parameter estimation process includes steps S420 to S440 described below.

In step S420, the parameter estimation unit 170 sets model parameters of the sensor detection torque estimation model 171. More specifically, the parameter estimation unit 170 sets model parameters of an N-mode (N is an integer of 2 or more). For example, the parameter estimation unit 170 sets a model parameter in an N mode following a normal distribution of the average value μ. The average value μ is, for example, the previous value of the estimated parameter F. Alternatively, the average value μmay be extrapolated from the previous value and the previous value of the estimation parameter F. The model parameters for the N-mode may also include nominal values.

In step S430, the parameter estimation unit 170 estimates the sensor detection torque MT using the sensor detection torque estimation model 171 based on each of the N-mode model parameters. The input to the sensor detection torque estimation model 171 is, for example, the motor rotation angle δ. Instead of the motor rotation angle δ, a motor target command torque or a target current value may be used.

In step S440, the parameter estimation unit 170 compares the estimated value of the sensor detection torque MT with the actual value of the sensor detection torque MT. The parameter estimation unit 170 extracts, as the optimal parameter, the model parameter that has obtained the estimated value closest to the actual value. For example, the parameter estimation unit 170 calculates a difference between the actual value and the estimated value, and extracts a model parameter having the smallest difference as the optimum parameter. Then, the parameter estimation unit 170 outputs the extracted optimal parameter as an estimation parameter F.

6-3 example 3

As described above, the upstream friction estimating unit 152 estimates the upstream friction torque TF (see fig. 4 to 9). The parameter estimation unit 170 may estimate a friction term (estimated parameter F) of the model of the steering system based on the upstream friction torque TF estimated by the upstream friction estimation unit 152.

Claims

1. A vehicle control system mounted on a vehicle, wherein,

the vehicle is provided with:

a wheel;

a steering wheel; and

a steering mechanism coupled to the steering wheel via a steering shaft, and configured to steer the wheels in accordance with a rotational operation of the steering wheel,

the vehicle control system includes:

a torque sensor that detects a torque applied to the 1 st position of the steering shaft as a sensor detection torque; and

a control device for performing automatic steering control for steering the wheels,

the upstream friction torque is an absolute value of the sensor detection torque caused by a friction force acting on the steering shaft between the 1 st position and the steering wheel when the steering shaft is rotated,

the intervention state is a driver state in which a driver of the vehicle intervenes in a steering maneuver of the vehicle,

the non-intervention state is a driver state other than the intervention state,

the control device performs the following processing:

a driver state determination process of determining that the driver state is the intervention state when the absolute value of the sensor detection torque is larger than the determination threshold, determining that the driver state is the non-intervention state when the absolute value of the sensor detection torque is equal to or smaller than the determination threshold,

the control means determines whether the driver has evacuated his hands from the steering wheel,

the control device performs the upstream friction estimation process in a case where the driver evacuates the hand from the steering wheel in execution of the automatic steering control,

in the upstream friction estimation process, the control device estimates an absolute value of the sensor detection torque at the time when the steering wheel starts to rotate by the automatic steering control, as the upstream friction torque.

2. The vehicle control system according to claim 1,

in the upstream friction estimation process, the control device estimates, as the upstream friction torque, half of a hysteresis width of the sensor detection torque accompanying the automatic steering control.